A unique aspect of nuclear reactors and a foremost safety consideration, is the inherent presence of radiation and radioactive materials. This highly significant condition requires the most strict design and safety conditions with respect to many components and functions of a nuclear reactor plant and imposes numerous requirements in operating and maintaining nuclear plants. For example, reactor components and related equipment which become significantly radioactive in service generally must be capable of long term, trouble free and positive functions, as well as being amenable to operation and maintenance by personnel in remote locations.
Steam depressurization and/or pressure relief valves or means are especially critical devices in any type of high pressure hot water and/or steam producing units, and when employed in a nuclear reactor plant the standards and demands must be applied to design and fabrication of such valves.
Various valve designs and operating modes have been proposed and considered in an effort to meet the stringent demands for such steam depressurization and pressure relief valves. For example, one proposed category of depressurization valves has been explosive/propellant-activated valves. In theory this type of valve should comply with the required design properties. This type of valve is fast operating, and routine valve maintenance and replacement of consumed parts of an opened valve can be quickly performed. However, it appears that with such explosive/propellant-activated valves, there are significant concerns such as limits upon the effective life of the explosive material as a result of exposure to heat and radiation, and flow rates obtainable with the current designs.